1. Field of the Invention
The present invention relates to a disc cartridge accommodating a disc that is an information recording/reproducing medium, and protecting a recording surface thereof from contaminants, such as dust or a fingerprint.
2. Description of the Related Art
In general, disc cartridges accommodate discs that are information recording/reproducing media and are loaded in disc drives. As shown in FIG. 1, a conventional disc cartridge 100 includes upper and lower cases 103 and 101 accommodating a disc D therebetween, and a shutter 110 rotatably installed on the lower case 101 to selectively open and shut an aperture hole 102 formed on the lower case 101 so that a pickup (not shown) of a disc drive can access the disc D. An open hole 103b is formed on the upper case 103 to exchange and clamp the disc D. An escape prevention lever 103a is slidably installed at the upper case 103 to prevent the disc D from escaping through the open hole 103b. Thus, when the disc D is installed in the disc cartridge 100, the escape prevention lever 103a is pushed back so as not to interfere with the disc D. When the installation of the disc D is completed, the escape prevention lever 103a is pushed forward as shown in FIG. 1, so that a tip end portion of the escape prevention lever 103a prevents the disc D from escaping through the open hole 103b. 
When the disc cartridge 100 having the disc D is inserted into the disc drive (not shown) as shown in FIG. 2A, an opening lever 120 installed at the disc drive first pushes a locking piece 111a so that a protrusion 111c of the shutter 110 and a groove 101a of the lower case 101 are unlocked. Next, as shown in FIG. 2B, the opening lever 120 pushes an interference piece 111b so that the shutter 110 pivots around left and right rotation shafts 110a. The shutter 110 is installed to rotate around the left and right rotation shafts 110a and includes first and second shutter portions 111 and 112 that are engaged with each other through an engagement gear portion 113. When the first shutter portion 111 integrally formed with the interference piece 111b rotates clockwise, the second shutter portion 112 rotates counterclockwise so that the first and second shutter portions 111 and 112 are separated from each other, and the aperture hole 102 is open.
Then, a turntable (not shown) and a damper (not shown) of the disc drive enter the aperture hole 102 and the open hole 103b, respectively, to clamp the disc D. Next, the pickup accesses a recording surface of the disc D to record and/or reproduce information on/from the recording surface of the disc D. Although not shown in the drawings, a torsion spring elastically biasing the first shutter portion 111 counterclockwise, that is, in a direction in which the aperture hole 102 is shut, is installed at the rotation shaft 110a between the first shutter portion 111 and a bottom surface of the lower case 101. Accordingly, when a force applied by the opening lever 120 is removed, the shutter 110 is returned to an original shut state.
However, in the above-described structure, a possibility that the recording surface is contaminated by dust coming through the open hole 103b of the upper case 103 is high. Of course, since an upper surface of the disc D facing the open hole 103b is not a recording surface, the contamination by dust does not directly affect the recording surface of the disc D. However, when the dust comes in the disc cartridge 100 and accumulates on the shutter 110, the dust on the shutter 110 adheres to the recording surface of the disc D during an opening/shutting operation of the shutter 110.
Also, the shutter 110 is installed between the upper and lower cases 103 and 101, the disc D is placed on the shutter 110, and the recording surface of the disc D (a lower surface of the disc in the drawing) and the shutter 110 make a surface contact during the opening/shutting operation of the shutter 110, thereby causing a damage, such as a scratch, on the recording surface of the disc D. Therefore, a structure which can prevent introduction of the dust and protect the recording surface of the disc D from the dust is needed.